The processing of oil shale and bitumen (tar sands) to produce commercially viable products has long been desired. However, existing shale or bitumen technology for recovering viable petroleum products contained therein is not economically feasible. In addition, spent shale or tar sand is a waste material that has not been constructively used.
An exemplary process for recovering oil from oil shale involves retorting oil shale so that the kerogen molecules are cracked. Inorganic matter of the shale must be separated from the heavy, highly unsaturated, highly viscous components. These fluidic components must be further processed by cracking, hydrocracking, hydrogenating, or by other processes.
FIG. 1 shows a known fixed bed process for treating oil shale. The temperature conditions and flow rates of the materials described are only provided for illustration and are not intended to be limited to those values. According to the process of FIG. 1, oil shale from a mine 10 (180,000 tons/day or 7,500 tons/hour) is conveyed via a bucket elevator 12 to a feed hopper 14. Raw shale in feed hopper 14 is maintained at about 60.degree. F. and is charged through feed valve 16 into a pressure equalizer 18. The shale is then conveyed through valve 20 into reactor 22 where hydrogen at 600 psi is introduced into reactor 22 at several locations.
Reactor 22 may be of any conventional design and, in particular, has a diameter of about 12 feet and a height of about 100 feet. Hydrogen is conveyed through line 26 and controllably introduced into reactor 22 via control valves 24. The hydrogen in line 26 comprises recycle and make-up hydrogen at a temperature of approximately 910.degree. F. The shale is processed in the reactor to produce synthetic crude, bi-products, hydrogen for recycling and spent shale.
Shale is discharged from reactor 22 through line 28 at a temperature of about 900.degree. F. and at a rate of about 6,750 tons/hour. Synthetic crude, bi-products and recycle hydrogen at 850.degree. F. are discharged from reactor 22 through flow line 30. The products in flow line 30 are conveyed to and introduced into heat exchanger bank 32 concurrently with make-up hydrogen plus recycle via flow line 72, whereby heat is transferred from the process products in line 30 to the hydrogen from line 72.
Cooled products from exchanger 32 are conveyed to cooler 36 and are thereafter introduced into a condensate drum 42. The bottoms from the condensate drum 42 include synthetic crude and bi-products that are removed and sent to a syncrude stripper 48 concurrently with a stripping hydrogen stream in line 70 from hydrogen source 66. The products from stripper 48, e.g., syncrude, are removed via line 49 at 180,000 barrels/day. A top product from stripper 48 is conveyed via line 50 to a bi-products recovery plant 52.
In bi-products recovery plant 52, elemental sulfur is produced and removed through line 58. Anhydrous ammonia (NH.sub.3) is also produced and removed via line 60. A hydrogen stripping stream is produced in plant 52 and is removed via line 62 and thereafter introduced into line 72 for recycling and use in exchange bank 32. Hydrogen that is produced in plant 52 is removed through line 54 and thereafter introduced into line 72. In addition, all the product streams from plant 52 are processed in a manner known to those skilled in the art to remove sulfur compounds to obtain useable products. The disadvantage of the process described by FIG. 1 is that it is not a continuous process.
In another known process for converting kerogen of oil shale to oil petroleum products, U.S. Pat. No. 4,153,533, a mixture of oil shale and hydrogen is subjected to wave energy in the microwave range to obtain oil.
In these and other oil shale and tar sands processes, the feed material must be mined. As a result, the sites that are mined/excavated to produce the feed for these processes are left untreated, resulting in depleted and non-usable land.
Thus, a need exists to provide a continuous process for treating oil shale and/or tar sands that is economical. A need also exists for practical use of spent product wastes that are generated from these processes. The present invention eliminates the drawbacks and limitations of batch or fixed bed type oil shale or tar sand conversion processes, as well as, the problems encountered when dealing with waste materials from these processes.